1. Field of the Invention
The present invention relates to copolymers of ethylene, carbon monoxide, and one or more termonomers copolymerizable therewith to produce UV-stabilized plasticizers.
2. Description of Related Art
WO 97/01114 relates to contact and intra-ocular lenses containing absorbers of ultraviolet (UV) radiation and methods thereof, by polymerizing a mixture of vinyl monomers, initiators, cross-linking agent and polymerizable UV absorbers.
U.S. Pat. No. 5,494,885 discloses a protective layer transfer film comprising a substrate film and a resin layer which comprises copolymer of an UV-absorbing agent and at least one of acrylic monomers, oligomers, and reactive polymers.
U.S. Pat. No. 4,528,311 discloses optically clear UV-absorbing copolymer compositions comprising up to 20 weight percent of 2-hydroxy-5-acrylyoxyphenyl-2H-benzotriazoles for UV-adsorbing films that afford 85% absorption at 400 nanometers and 1 millimeter thickness, which may be added to other organic materials to impart ultraviolet absorbing properties thereto. Variations of the copolymers are described in Specialty Chemicals Vol. 16, No. 2, March/April 1996 as novel bondable stabilizers.
U.S. Pat. No. 3,780,140 relates to copolymers of ethylene/carbon monoxide/termonomer, and polymer blends formed therefrom for use as plasticizers in plastics such as polyvinyl chloride (PVC), nitrocellulose, etc. The ethylene copolymers are routinely used in PVC formulations for use in melt-processible rubbers, flexible PVC sheeting, pond liners, and membranes.
Traditionally, UV stabilizers are added to the formulations during the melt compounding step. UV stabilizers that absorb radiation in the 200 to 400 nm range are most frequently employed. The most frequently employed UV stabilizers are those of the substituted 2-hydroxybenzophenone and benzotriazole types, in sufficient concentration to provide adequate stability against exposure to UV light. The UV stabilizers are typically added to the formulation during the melt-compounding step, meaning that they are added to the mix in a mixer, extruder, or similar devices. As such, these stabilizers do not attach to the polymers such as through covalent bonding. Consequently, they are not permanent and can be lost through extraction, volatilization, or migration. Analysis of sample PVC-based rubber bulbs for use in portable gasoline cans, which failed prematurely by embrittlement during usage, showed that none of the originally added benzotriazole UV stabilizer originally added to the formulation was still present. It is assumed that the gasoline had extracted the stabilizer from the rubber bulbs, thus causing the premature failure.
Thus there is a need for UV stabilized ethylene copolymer compositions as plasticizers or in alloys and blends with other polymers, that are resistant to UV degradation and/or weathering even after extended periods of time in use.